The invention relates to a rear wheel hub, in particular for bicycles. In the field of sports including semi-professional and also professional cycling, rear wheel hubs for bicycles as a rule allow the user to employ many different transmission ratios. In most cases, chain shifting devices are employed where a plurality of sprockets is disposed at the rear wheel hub to allow the different transmission ratios. To ensure an optimal riding style e.g. in steep downhill rides a freewheel is provided to enable the rider to let the bicycle roll without pedaling.
In the field of high quality cycling the stressability and weight play a major role. The users consider it important to have high-grade components that are easy to maintain where each gram of weight counts.
In the prior art, rear wheel hubs with different freewheels have been disclosed. From DE 198 56 627 A1 for example a rear wheel hub having a ratchet freewheel has become known where drive torque is transmitted via ratchet pawls from the rotor to the hub shell. It is a disadvantage of such hubs that in assembly the freewheel pawls must be inserted separately which will result in a large amount of time and work for regular, e.g. daily, maintenance. Also these hubs are comparatively heavy.
A simpler assembly and maintenance is provided by a rear wheel hub known for example from DE 198 47 673 A1 where torque is transmitted through a pair of toothed discs provided with axial, meshing toothing at their adjacent side faces. The torque applied is reliably transmitted in the drive direction while in the opposite rotational direction the toothed discs axially diverge from one another, thus allowing freewheeling.
A freewheel must be configured for high torque loads of up to 400 Nm and higher to reliably transmit the loads occurring. This is a torque which e.g. in automobiles will not occur in the usual family cars but e.g. in sports and racing vehicles. To reliably transmit these very high loads, the toothed discs of the freewheel in the known hub are massive, of solid material. The disadvantage is the comparatively high weight of the toothed discs which constitutes a substantial portion of the total weight.
It is therefore the object of the present invention to provide a rear wheel hub which combines a low weight with easy maintenance without impairing durability.